1. Field
The invention is in the field of adjusting the tension of the primary chain in a motorcycle.
2. State of the Art
Most motorcycles have a primary chain that extends between a clutch sprocket and an engine compensating sprocket. The clutch sprocket, engine compensating sprocket, the primary chain, and a chain adjusting shoe assembly are located in a primary chain case having a primary chain case cover and a primary chain adjustment inspection cover. The lower span of the primary chain between the sprockets rides on a chain adjustment shoe of the chain adjustment shoe assembly and the chain adjustment shoe is mounted for up and down adjustment movement within the primary chain case through an adjusting shoe mounting bracket and attaching bolt. The adjustment shoe and mounting bracket can be moved up and down by loosening the bolt. Movement of the shoe adjusts the tension of the chain. This arrangement is used, for example, in Harley Davidson motorcycles with Evolution 1380 cc and 1488 cc engines. In such motorcycles, the primary chain adjustment inspection cover is removed to expose the bolt and enough of the adjustment shoe bracket to allow loosening of the bolt and movement of the bracket, which moves the adjustment shoe, for adjustment of the primary chain. However, the primary chain is not exposed with removal of the primary chain adjustment inspection cover.
Instructions from the Harley Davidson Motorcycle Handbook tell the motorcycle owner to “Inspect the chain periodically for cracked, broken or badly worn links. Chain adjustment must be inspected every 5000 miles (8000 km). As chains stretch and wear they run tighter at one spot than another. Always adjust free movement at the tightest spot in the chain to allow specified play midway between sprockets. Do not adjust tighter. Running chains too tight will result in excessive wear.” The instructions then tell the owner that “Primary chain tension is adjusted by a shoe located in the primary chain case. The shoe is raised or lowered to tighten or loosen the chain. The chain should have free up and down movement in the upper strand midway between the sprockets. This deflection should be ⅝-⅞ in. (15.9-22.3 mm) with the engine cold and ⅜-⅝ in. (9.5-15.9 mm) with the engine hot.” However, since the chain itself is not visible in the primary chain case with the primary chain case inspection cover removed, it is difficult to determine the play in the upper strand between sprockets.